Entertainment systems currently use a variety of different audio sources. Here, each audio source typically has a specific volume level which is predefined by the respective hardware, the software that is used, and the audio track concerned. After changing the audio source, the user is normally compelled to adjust or readjust the main volume in order to achieve the same, subjectively perceived, volume as previously. The perceived volume, which is known by the term “loudness”, is dependent on the frequencies, amplitudes and temporal position of the audio signals.
According to the online encyclopedia Wikipedia, loudness is a quantity for the proportional mapping of human volume perception (cf. http://www.wikipedia.de under the heading “Lautheit” [“Loudness”], version dated Aug. 3, 2015).
Loudness is a psychoacoustic term which describes how a number of test persons predominantly assess perceived volume. Loudness depends on the sound pressure level, the frequency spectrum and the behavior over time of the sound. The perception of loudness is caused by the type and manner of the sound processing in the inner ear. Depending on the strength of the excitation of the nerve cells, a noise is assessed as louder or quieter. Loudness will generally be twice as great when the sound is perceived as twice as loud.
Standardized measuring methods are known for the quantitative determination of loudness. However, the term “loudness” used in the context of the present disclosure is generally intended to be understood as a psychoacoustically weighted volume which may correspond to loudness (measured in sones) defined according to standardized measuring methods, but can also be defined by means of alternative (where appropriate simplified) methods.
Algorithms are known which adjust the volume of audio signals during real-time processing. However, these algorithms change the sound track concerned using equalizers, compressors or limiters, or they reduce the dynamic range as a result of the adjustment. In addition, algorithms of this type frequently require a high processing and storage capacity.